1. Field of the Invention
The present invention relates to a document composition apparatus which forms character patterns by using outline fonts.
2. Description of the Related Art
In recent years, document composition apparatus which hold the image of the character pattern of a character in the form of a dot pattern, or dot font have been extensively used.
More recently, document composition apparatus that have an outline font function for character patterns, to form higher quality character patterns, have been produced. One of them is a Desk Top Publishing (DTP) device.
In general, a character pattern formed by an outline font can be represented by straight lines and/or curved lines. There have been several methods proposed for representing the shape of a character pattern. One of these is a technique in which both straight line segments and curved segments are approximated by short line segments. Another such method approximates straight line segments by short line segments, and approximates curved portions by fitting a so-called Bezier Curve, which actually is a series of short line segments closely approximating the curve, to the curve. A description of these methods can be found in "Digital Formats for Typefaces" by Peter Karow 1987.
The latter method represents all the shapes of character patterns by approximation, by means of short line segments using the simplest technique and minimizing the amount of complex calculation for the approximation. Therefore, in terms of hardware, an apparatus of such a type is simple and capable of high-speed processes. Thus, formation of the character patterns including enlargement, reduction, rotation, and the like, can be efficiently carried out.
Further, when using the method of approximation in which short line segments are used for the straight line portions and Bezier curves are fitted into the curved portions, a curved portion can be represented accurately by continuously following the change in curvature. Therefore, even if a character is greatly enlarged, a smooth curved line can still be drawn. However, the calculation necessary for fitting Bezier curves into the curve portion is enormous, and much time is required for forming a character pattern, making it difficult to do this in real time.
In this related art, the curved portions have been represented by a particular single method. A different problem occurs with either one of the above-stated methods. In the case of short line segment approximation, the quality of a character deteriorates when the character is enlarged a great amount, or in the case of Bezier curve approximation, much more time is required for fitting the Bezier curve into a curved portion than in the case of short line segment approximation.